Biomechanics for Trabecular Architecture and Fracture Mechanism of Osteoporotic Cancellous Bone

骨质疏松症降低了骨密度，并使其容易导致骨折。骨密度是一个所谓的各向同性变量。因此，骨密度不能呈现强度的差异，这取决于结构的各向异性的区别。股骨颈骨折是在不同方向和强度的力的作用下发生的。尽管如此，颈部骨折类型仅限于典型和新月形骨折类型中的2种。这个原因是骨质疏松症改变小梁结构（细胞结构的大小和形状）的原因。同时比较股骨头外侧、主压缩组和内侧松质骨的压缩极限强度和组织形态计量学参数。阐述了骨质疏松症导致股骨颈囊内骨折这一典型骨折类型的骨折机制。另一方面，采用双能X线骨密度仪（DEXA）测定骨质疏松症患者腰椎及股骨近端各部位的骨密度，并分析其与松质骨力学强度的相关性。结果，可以理解，只要我们仅用BMD进行判断，即使我们指出骨质疏松的倾向，也不可能在指定如股骨颈和椎体的位置时预测骨折。松质骨的各向异性程度可以通过计算机图像处理从简单的X射线图像估计。因此，通过对骨密度测量的力学特性和松质骨结构各向异性的累积结果进行综合判断，可以构建骨折的预防诊断系统。

Osteoporosis decreases a bone density and makes it easy to cause fracture of bones. Bone density is a so-called isotropic varriable. Therefore, bone density can not present a difference of strength that depends on a distinction of anisotropy of the architecture.The femoral neck fracture occurs by force with various directions and intensity. In spite of this, the neck fracture type is limited to 2 kinds of in the typical and the crescent fracture type. This reason is a cause that osteoporosis changes a trabecular architecture (size and shapes of the cell structures). Simultaneously, we compared compression ultimate strengh and the histomorphometric parameters of the lateral, the principal compressive group and the medial cancellous bone in the femoral heads. Then we explained the fracture mechanisms which osteoporosis induces the typical fracture type of the intracapsular femoral neck fracture. Other hand, also we measured the bone mineral density (BMD) of the lumbar veretebrae and the every part in the proximal femur of osteoporosis patients by the DEXA.We analyzed correlation between BMD and the mechanical strength of the cancellous bone that were obtained through the experiment. As a result, it understood as long as we judges with only BMD,even we point out a tendency toward osteoporosis, it is impossible to predict a fracture while designating a place like a femoral neck and a vertebral body.A degree of anisotropy of the cancellous bone is possible estimation from the simple X-rays images by way of computer image processing. So we will be able to construct a prevention diagnosis system of bone fractures by judging and integrating the accumulation result of the mechanical properties which come from BMD and the anisotropy of the cancellous structures.